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Species with big sex differences are more likely to die out

By Alice Klein

THE peacock’s tail may dazzle females, but such extreme ornaments can reduce males’ chances of surviving to such an extent that the whole species is far more likely to die out.

Sexual selection by females can lead to the evolution of extreme traits in males, from colourful plumage to extravagant displays. Biologists have long debated how this affects the long-term survival of species.

Some think extreme sex differences make species more vulnerable to extinction, because they require lots of resources and make it harder to evade predators. The counter argument is that they ensure only males with …